Contact mounting for electrical switches



July 18, 1950 s. D. VIGREN ETAL 2,515,914

CONTACT MOUNTING FOR ELECTRICAL SWITCHES Filed Sept. 7, 1945 2 Sheets-Sheet 1 Fig.3

Patented July 18, 1950 CONTACT MOUNTING FOR ELECTRICAL SWITCHES Sten Daniel Vigren, Stockholm, and Walter Otto Wilhelm Broberg and Oscar Karl Johan Olsson,

. Nynishamn, Sweden, assignors to Telefonaktiebolaget L. M. Ericsson, Stockholm, Sweden, a

company of Sweden Application September '7, 1945, Serial No. 615,035 In Sweden May 25, 1943 The invention relates to contact devices for electric switching devices of the cross-bar type, in which movable contacts are provided to cooperate with a number of spaced contact points fitted along stationary carrier strips of insulating material.

In such electrical switching devices the contact spring sets are frequently arranged to be operated by lifting studs produced by a milling or pressing operation, the spacing between the contact springs being maintained with great accuracy. In order that, without involving undue work in setting or difiiculties in manufacture, all movable contacts on operation of the spring sets engage the fixed contact points simultaneously and with equal contact pressure, the spacing between the fixed contact strips must be as accurate as the spacing between the movable contact springs.

. Previously, the fixed contacts have been inserted in metal strips which are separated by means of insulating spacers, the unit formed by these metal strips and spacers being assembled with the aid of screws to form a rack. In this type of device, however, the drawback prevails that the limits of the manufacture of the metal strips and of the spacers and their relative expansion involve difficulties in uniform and accurate spacing. It has been necessary, therefore, in cross-bar switches, to make adjustable the individual parts of the metal strips which carry the contacts.

The present invention makes it possible to obtain as accurate a spacing between the fixed contact points supporting the strips as the spacing between the movable contact springs, and considerable advantages are also gained in regard to both simplicity and quantity of manufacture.

In accordance with the invention the stationary carrier strips are inserted in holes in a number of supporting members for supporting the carrier strips, each strip, in relation to only one of said supporting members, thus bein rigidly arranged in the longitudinal direction of the carrier strip so that possible longitudinal changes in the length of the carrier strips may take place freely.

In order that the invention may be clearly understood and readily carried into effect, the same will hereinafter be more fully described with reference to the accompanying drawings in which:

Figure 1 is a vertical front view of the contact arrangement; and

Figures 2 and 3 are respectively plan and side views thereof.

Figure 4 is a fragmentary perspective view in 1 Claim. (Cl. 200-166) which some of the parts are shown in dotted lines.

The contact strips B are formed as thin metal strips fastened by small tongues or tabs C to a strip A of insulating material which at the same time serves as a support. The rack is formed by an upper plate T and a lower plate D with suitable ears E for connection to the relay or the switch. A number of support plates F, F1, F2, F3 of metal are riveted to the plates T and D, holes being pressed in said plates with the same spacing as the spacin of the lifting stud K. The holes are made so that the insulating strips fit into them easily but without excessive clearance. In a crossbar switch, for example, the two extreme support plates F1 and F2 are provided with pressed holes so that the strips are guided in all directions except in their longitudinal direction. The intermediate distance plates F, F3 are formed only to control the strips vertically. The mounting arrangement is such that the strip is introduced in the distance plate F1 so far as to bring the other end of the strip inside the support plate F2. The strip is then fitted between the camshaped support plates F, F3 and thereafter pushed forward longitudinally so that the end of the strip projects somewhat beyond the outer distance plate F2. Mounted in that manner, the strip is guided in all directions except the longitudinal direction. When all the strips are mounted they are fixed by passing a small pin G through openings A, formed in all the insulating strips A and the support plate F3 which has specially shaped portions H to hold the pin against lateral displacement when the pin has been pressed down into position the topmost portion H1 of the plate F3 is folded over the pin G to prevent the pin from falling out. The strips are now fixed in their longitudinal direction as well as in other directions the portions H and H1 forming as it were a comb on the plate Fa.

t This construction offers the followin advanages:

The arrangement requires few components, all of which are simple and inexpensive to manufacture.

The assembly is easily effected, no screws being required.

Circuit connections to the contact strips may be made by soldering and for this purpose one extremity of the contact strip is formed as a soldering tag Cl, which passes through a slot in the insulating strip and projects through the upper side thereof, where it is bent over. A construction of this kind excludes the risk of fluxing material from the solder flowing over the surtag is sufficiently supported by and secured in the insulating strips.

The spacing between the contact strips. is as. accurate-asv between lthe contact springs S. perience proves that an appropriate fitting of the contact springs and a special adjustment of the same before their assembly gives a contact pressure the tolerances of which are satisfactory Without necessitating adjustment during assembly. Should, on some special occasion, adjust! ment be required, this maybe-performed on themovable contact springs S.

By suitably arranging the fixing tongues or'tabs C, the movable contact springs, in the inactive position, can press against the-underlying insulating strips. with metal strips, it is thus not necessary to allow for a pre-determined distance between the movable springs and the -underlying strip. Consequently,. the. arrangement providesv smaller spacing; between the. contact springs than in previous constructions, without involving. any inconveniences..

, The device isunafiectedby changes in temperature or. humidity of'the air. This isachieved by making the tongues or tabs 0, smaller than the holesin theinsulatin strip, so that the latter may contract or. expand withoutcreating anyrelative pressure. between a metal strip. and an insulating. strip. Longitudinal. positioning; of the. insulating strip,.fur.thermore, is provided at one point only, which is approximately central, so .that longitudinalexpansion of the strip. may. take. place freely. Eventually occurring'lateral deflection of the'stripis preventedby the two outersupport plates,F1,.Fz and by pin G.

The. invention may be. varied and .modified in many ,diiierentways .within: the scope of the appendedaclaims. One or several contact strips, for example, may instead. be arranged to provide breakcontact. Individual contacts may be pro-v vided for each contact spring. Instead of the. metal contact strip, aplate ofcontact material is inserted; in. each contact. point, .said .contact ma-v Contrary to previous constructions Number Name Date 1515,6312? Taylor .Nov.1 18,' 192g 1,645,897 Crowe Oct. 18; 1927 2,127,322 Blomberg; Aug. 16,1938 2.134;448 Oct. 25,1938 2,279,811 Baker: Apr. 14,- 1942 2,282,687; Vigren .et a1. May: 12,1942. 2,348,088, Nicholsetal; May 2.3.1944:

terial being provided with a soldering tag, used also as a fixing pin, to which the connection is soldered. The insulating strip is in principle of the same design... as when. complete metal strips are. used.

The support plates F, F1, F2 and F3 which above are assumed to be of metal, may naturally also consist of insulatin material. The contact strips maythereby, if required, be made entirely of conducting material.

Weclaim:

I In a contact arrangement for electrical switches otthe cross-bantype, stationary carrier strips of insulating material;.;a plurality of spaced contact points alongeachof said strips, a corresponding plurality of movable contacts cooperating with said, spaced contact points, a, plurality of supporting members common to said carrier strips and having apertures in which said strips are inserted, each strip beingtransfixed at one point only of its .lengthnoincident withtone of" said .sup- P rting. members, .so that longitudinal expansion and contraction of. the carrier. strip; may: take. place freely with respecttorsaid point; one .of sa'id support" members having lugs. and at member passing through said lugs and said stripstcpse, cure: said strips fixed; at'one pointonly;

STENJDANIEL VIGREN.; WALTER OTTO .WILHELM' BROBERGe'. OSCAR JOHAN OLSSON.

REFERENCES. CITED.

The following references are of record in the file" ofthis patent UNITED. STATES PATENTS 

